Process for producing aromatic hydrocarbons



Patented Aug. 16, 1932 UNITED STATES HARRY K ARL IHRIG, OF PITTSBURGH, PENNSYLVANIA PROCESS FOR PRODUCING AROMATIG HYDROGARBONS No Drawing. Application filed June 15,

This invention relates to the improved method of segregating the aromatic hydro carbons and their derivatives in the treatment of hydrocarbon oils.

In the refinement of gasoline, kerosene, or the like, a polar solvent is often used to extract impurities such as aromatic, hydroaromatic and unsaturated hydrocarbons. The separation of the saturated aliphatic hydrocarbonswhich are called rafiinat, or refined petroleum products-from the aromatic, hydroaromatic. and unsaturated hydrocarbonswhich are called the extractis only a moderately eflicient one. Since the extract is the starting point of this process, the incomplete separation in this treatment, namel the presence of the saturated aliphatic hydrocarbons therein, presents a serious problem.

Therefore, the object of this invention is to eliminate the saturated aliphatic hydrocarbons from the extract and thereby obtain a maximum amount of aromatic hydrocarbons in their purest form.

Certain crude petroleums and pressure distillates contain large quantities of aromatic hydrocarbons and it is with these that this process deals primarily. These aromatic hydrocarbons are generally objectionable and are eliminated by. reason of their solubility in a polar solvent, such as liquid sulphur dibxide, liquid ammonia, or liquid hydrogen chloride. Such polar solvents are referred to herein as those of the liquefied gas type. In the treatment of hydrocarbon materials with a polar solvent;

such as liquid sulphur dioxide, the attention of those interested in the art has heretofore been directed to the raflinat, which contains the saturated aliphatic hydrocarbons, while the extract has been used for a cheap fuel,or was discarded. It has been found that this extract contains many valuable products, but the presence of the saturated aliphatic hydrocarbons in such extract has preventedtheir economical recovery and utilization prior to my invention.

Ordinarily, in order to assure the-elimi nation of all of the impurities, such as aromatic, hydroaromatic an d unsaturated 1927. Serial No. 199,116.

hydrocarbons, from the rafiinat, the separation has been carried on at temperatures high enough so that some of the saturated aliphatic hydrocarbons are lost in the extract. The presence of a relatively small proportion of saturated'aliphatic hydrocarbons when mixed with aromatic, hydro aromatic and unsaturated hydrocarbons interferes materially with the satisfactory utilization of the aromatic constituents, in that they affect the distillation and nitration steps that follow. I have found that these saturated aliphatic hydrocarbons in the extract are practically eliminated by retreatment with liquid sulphur dioxide at low temperatures. This is highly important, because the separation of the various groups of aromatic hydrocarbons is best accomplished by fractional distillation, and as there are saturated aliphatic hydrocarbons and aromatic, hydroaromatic and unsatu rated hydrocarbons boilin at the same temperature, it is practically lmpossible to separate them by fractional distillation alone, and this has militated against the commercial use of the extract.

In the extract are concentrated the aimmatic, hydroaromatic andunsaturated hydrocarbons, together with a small quantity of, saturated aliphatic hydrocarbons. The liquid sulphur dioxide is washed out with water and the remainder of the extract is treated with sulphuric acid, which eliminates the unsaturated hydrocarbons. Sulphuric acid of approximately 85% purity 1s used because the reaction between certain hydrocarbons and strong sulphuric acid is so vigorous as to polymerize or change them, causing loss of valuable materials, whereas if an acid of less strength is used these relatively reactive hydrocarbons are not attacked. By this elimination of the liquid sulphur dioxide and the unsaturated hydrocarbons, a smaller volume of extract, conslsting of-aromatic,.hydroaromatic and the objectionable saturated aliphatic hydrocarbons, remains. this'material is then treated with a polar solvent of the liquefied gas type to separate the In accordance with the invention V non-polar hydrocarbons.- In the preferred '9 practice of the invention the thus-treated extract is treated with a large-proportion of sulphur dioxide at approximately 0 F. to reduce the saturated aliphatic hydrocarbons to a minimum. It has been found necessary in this additional treatment with liquid sulphur dioxide to use an amount nearly equal to the volume of hydrocarbon material to be treated, but preferably a very considerable excess of the liquid sulphur dioxide should be used. The extract from this second extraction is washed with water and then neutralized. This extract is steam distilled and fractionated, and the various fractions are nitrated, or otherwise treated to obtain the desired aromatic hydrocarbon products.

The step of nitration, for example, may be carried out by mixing with equal volumes of nitric'and sulphuric acid.

To demonstrate the utility of thisprocess, the following run was made:

500 gallons of gasoline from California crude was washed with 20 B. caustic soda to remove certain sulphur compounds, then dried and treated with 250 gallons of liquid sulphur dioxide at 0 F. four times in succession. 79.38% rafiinat, or saturated aliphatic hydrocarbons, and 19.29% of extract, or aromatic, hydroaromatic and unsaturated hydrocarbons, were recovered, with 1.33% loss. 42 gallons of the extract obtained from this treatment was treated with 55 pounds of 85% sulphuric acid, applied in three charges, drawing oil the acid sludge after each change. The remainder was then washed with water and neutralized with weak caustic soda, and 38% gallons remained to be treated. This was extracted with 150% liquid sulphur dioxide at 0 F. and 38.88%

saturated aliphatic hydrocarbons separated out in the upper layer, and 61.12% of extract was drawn ofi'. The extract had a gravity of 40 A. P. I, before the second extraction, and the saturated aliphatic hydrocarbons from the second extraction had a gravity of 472 A. P. I. The extract from the second extraction was neutralized with weak caustic soda and washed with water. This material was then ready for the fractional distillation and subsequent nitration as heretofore described.

To illustrate the diflerence in yields obtained, or, in other words, the superiority of the above described process from what could be accomplished from utilizin an extract obtained in the usual way, the ollowing ex; ample is given:

The original extract was nitrated with a mixed acid composed of 100% by volume of concentrated nitric acid and 100% b. volume of concentrated sulphuric acid, an 62% of the volume of the extract was nitrated. AfQr subjecting this same extract to the above process, the final concentrated extract upon nitration by the same method gave 81% by increased yield of 19% of nitrated material.

It must be understood that there is practically no additional cost to this re-treatment with liquid sulphur dioxide, as the sulphur dioxide is recovered and used again, thereby operating in a continuous cycle.

The term hydrocarbon material, as used herein, is intended to include all the distillates of crude petroleum such as gasoline, kerosene, lubricating distillates and the like, or an mixture thereof.

hat I claim is 1. A process of treating a mixture of saturated aliphatic hydrocarbons and aromatic, hydroaromatic and unsaturated hydrocarbons, comprising treating such mixture with a polar solvent of the liquefied gas type to form a solution containing said aromatic, hydroaromatic and unsaturated hydrocarbons together with a minor proportion of said saturated aliphatic hydrocarbons, separating said solution from the undissolved saturated aliphatic hydrocarbons, recovering the extracted material from said solution, treating said extracted material with a polar solvent of the liquefied gas type and thereby dissolving said aromatic, hydroaromatic and unsaturated hydrocarbons'and separating them as a solution in the solvent from the minor proportion of saturated aliphatic hydrocarbons contained in said extracted material, separating the last-named solution from. the residual undissolved saturated aliphatic hydrocarbons, and recovering the purified extract from said last-named solution.

2. A process of treating a mixture of saturated aliphatic hydrocarbons and aromatic, hydroaromatic and unsaturated hydrocarbons, comprising treating such mixture with a polar solvent of the liquefied gas type to form a solution containing said aromatic, hydroaromatic and unsaturated hydrocarbons together with a minor proportion of said s turated aliphatic hydrocarbons, separating said solution from the undissolved saturated aliphatic hydrocarbons, recovering the extracted material from said solution,.treating said extracted material with apolar solvent of the liquefied gas type, and thereby dissolving the aromatic, hydroaromatic and unsaturated hydrocarbons and separating them as a solution'in said solvent from the minor proportion of saturated aliphatic hydrocarbons contained in said extract, the volume of said further amount of said polar solvent being at least equal to the volume of the extract, separating the last-named solution from the residual undissolved saturated aliphatic hydrocarbons, andrecovering the purified ex tract from said last-named solution.

3. A process according toclaim 2, said nevneee polar solvent of the liquefied gas type comprising liquefied sulfur dioxide.

4. A process of treatin a mixture of saturated aliphatic hydrocar ns and aromatic, hydroaromatic and unsaturated hydrocarbons comprising treatin such mixture with a polar solvent of the liquefied gas type to form a solution containing said aromatic hydroaromatic and unsaturated hydrocar ns together with a minor proportion of said saturated aliphatic hydrocarbons, separating said solution from the undissolved saturated aliphatic hydrocarbons, recovering the ex tracted material from said solution, treating the extracted material with sulfuric acid to remove unsaturated hydrocarbons and separating the residual aromatic and hydroaromatic hydrocarbons from said minor rortion of saturated aliphatic hydrocar one by treatment with a polar solvent of the liquefied gas type in an amount such that the volume of said solvent is at least e ual to that of the extract being treated, and t ereby diasolvingsaid aromatic and hydroaromatlc by drocarbons and separating them as a solution in said solvent from said minor proportion of saturated aliphatic hydrocarbons, separating the last-named solution from the residual undissolved saturated aliphatic hydroa0 carbons, and recovcrin the aromatic and hydroaromatic hydrocar ons from said lastnamed solution,

5. A rocess of treatin a mixture of satu-= rated aliphatic hydrocar ons and aromatic,

1:5 hydroaromatic and unsaturated hydrocarbons', comprising treating said mixture with liquefied sulfur dioxide to form a solution containing the aromatic, hydroaromatic and unsaturated hydrocarbons together with a 10 minor proportion of said saturated aliphatic hydrocarbons, separating said solution from the undissolved saturated hydrocarbons re= covering the extracted material from sai solution, treating said extracted material with sulfuric acid to remove unsaturated hydrocarbons and treating the residual extract with a volume of liquefied sulfur dioxide substam' tially in excess of that of said residual extract to dissolve said aromatic and .hydrw to aromatic hydrocarbons and separate them as a solution in the sulfur dioxide from said minor proportion of unsaturated aliphatic a hydrocarbons, separating the last-named solution from the residual undissolved satu rated aliphatic hydrocarbons and recovering I the purified extract from said last-named solution,

Intestimony whereof I'signm name. HARRY i IHIRIG, 

